Is it known to encapsulate water insoluble perfumes or other materials, in small capsules often termed microcapsules, typically having a diameter less than 1000 micrometers (microns), for a variety of reasons relating to the protection, delivery and release of the perfume or other material. The preparation of microcapsules is described in Kirt Othmer's Encyclopaedia of Chemical Technology 5th edition and also in the following U.S. Pat. No. 2,800,457 and U.S. Pat. No. 3,415,758 and citations thereof and U.S. Pat. No. 6,261,483 and references therein. One type of capsule, referred to as a wall or shell or core shell capsule, comprises a generally spherical shell of water and oil insoluble material, typically a network polymer material, within which perfume or other material is contained.
If such capsules are incorporated in consumer products containing certain solvents and/or emulsifiers or surfactants, e.g. personal care products such as deodorants, hair sprays or shampoos, laundry products such as fabric conditioners or liquid laundry detergents and household cleaners such as kitchen surface cleaners, problems can arise with the encapsulated material tending to leach out of the capsules and be solubilised in the product over time diminishing the capsules delivery of their core materials.
U.S. Pat. No. 4,234,627 teaches the incorporation of hydrophobic non polymeric materials with the fragrance to control perfume release. However this involves a dilution of the fragrance or benefit agent.
US patent application 20060154378 relates to a method for measuring the leaching of encapsulated material in an application medium using a dialysis or filtration to separate the active ingredient molecules from the capsules.
US patent application 20050153135 teaches a variety of methods to reduce perfume leaching by formulating the fragrance from materials which are substantially water insoluble, by adding an oil or polymer to the fragrance to reduce the partitioning. While such measures reduce the rate of escape they do not prevent it and they may have other undesirable consequences such as reducing the impact of the fragrance.
US patent application 20060039934 teaches that adding polymers, either to the core contents prior to encapsulation, or the exterior of the capsules can reduce leakage. Again this adds to the cost and processing complexity involved in manufacturing capsules.
Notwithstanding these teaching terse is still a need for ways to minimize the loss of fragrance during storage and the present invention aims to address such stability problems.